Generally, sewing machines typically include a head which contains much of the sewing needle drive assembly and a base which includes a throat plate having a needle hole therethrough such that the needle may interact with other sewing components contained within the base. Many sewing machines also include a jump foot which is contained within the casting of the sewing machine and which engages/disengages the material being sewn on by the machine ("stitchable material") in a timed relation with the movement of the sewing needle. The jump foot functions as an "anti-flagging" device. Flagging is a condition which occurs when stitchable material and thread are pulled upwardly with the sewing needle after a portion of the sewing needle and thread have been driven down through the stitchable material and are thereafter being driven upwardly. Due to the frictional engagement between the sewing needle, thread, and stitchable material, the portion of thread adjacent a side of the sewing needle and below the stitchable material cannot sufficiently separate from the side of the sewing needle to form a loop through which an oscillating sewing shuttle hook can pick up the thread to form a stitch. As such, flagging can result in a poor stitching pattern and including having a sewing pattern with skips. Thus, in sewing machines having a jump foot, the jump foot functions to hold the stitchable material and a portion of the thread stationary relative to the upwardly moving sewing needle to separate the portion of thread from a side of the sewing needle to form a loop through which a sewing shuttle hook can pass to form the desired stitch.
Although many sewing machines do come with a jump foot assembly contained within the casting of the machine, a number of sewing machines do not have a jump foot. Some of these machines utilize a presser foot or the like which, during reciprocation by the sewing needle, always remain in contact with the stitchable material. That is, the presser foot does not move in a timed relation with the sewing needle. These machines will typically have a feed dog disposed under the stitchable material and the displaced feet of the presser foot to linearly advance the stitchable material.
One type of kit of sorts which has been utilized in the sewing industry to reduce problems with flagging is a needle plunger. A needle plunger is effectively a hollow tube which is concentrically mounted on the lower end of a needle bar such that the sewing needle extends and protrudes below the lower end of the spring-loaded plunger. As the needle bar is driven downwardly to make a stitch in the stitchable material, the spring-loaded plunger traps the stitchable material between the plunger and the throat plate, thus holding the stitchable material stationary relative to the reciprocating sewing needle. The plunger remains engaged with the stitchable material as the sewing needle is driven upwardly a sufficient amount of time to reduce the potential for flagging of the stitchable material. Although the needle plunger functions appropriately in many applications, as production speeds are increased, noise can become a problem, and mechanical difficulties may arise as well.